1. Field of the Invention
This invention relates to an improved wet strength polyurea polyurethane foamed product which can be used as a sponge.
2. Description of Previously Published Art
It has long been a goal of the sponge industry to substitute polyurethane foam for cellulose foam for use in wiping sponges or in sponge-based composites such as scrubbing pads or bathmats. In general, polyurethane foams of the previous art which are hydrophilic enough to be useful, tend to swell greatly when they are wet such as on the order of more than about 75-100% by volume. They dry slowly and nonuniformly, causing curling or cockling and they are aesthetically unacceptable.
In U.S. Pat. No. 3,806,474, a hydrophilic polyester urethane foam is disclosed. However, this foam has a large volume swell, it does not wet out rapidly and it does not wipe so as to leave a clean surface.
In U.S. Pat. No. 4,160,076, a simulated natural sponge based on hydrophilic polyurethane is disclosed. However, even though this simulates a natural sponge, it still has the problem like that of the natural sponges of a great amount of swelling when it is wet.
3. Objects of the Invention
It is an object of this invention to produce a polyurethane foam which behaves like a cellulose sponge with a volume swell of less than about 50% when wet, and preferably less than 35%.
It is a further object to add to a polyurethane foam forming composition the proper combination of additives to make the sponge stronger, less swellable, more rapidly wettable, and more durable.
These and further objects will become apparent as the description of the invention proceeds.